This invention relates to a microfluidic systems and method for mixing, regulating, delivering, transporting, and storing minute quantities of liquids.
Microfluidic systems are very important in several applications. For example, U.S. Pat. No. 5,445,008 discloses these systems in biomedical research such as DNA or peptide sequencing. U.S. Pat. No. 4,237,224 discloses such systems used in clinical diagnostics such as blood or plasma analysis. U.S. Pat. No. 5,252,743 discloses such systems used in combinatorial chemical synthesis for drug discovery. U.S. Pat. No. 6,055,002 also discloses such systems for use in ink jet printing technology.
The so-called xe2x80x9cLab-on-a-Chipxe2x80x9d generally refers to a microfabricated device of microfluidic systems that regulate, transport, mix and store minute quantities of liquids rapidly and reliably to carry out desired physical, chemical, and biochemical reactions in larger numbers. Those devices have been disclosed in U.S. Pat. No. 5,876,675, No. 6,048,498, and No. 6,240,790 and European WO 01/70400. One of the most important issues in the lab-on-a-chip devices is the moving and mixing of multiple transport fluids inside the chip in a controlled fashion. Several methods of transferring and controlling of liquids have been disclosed by U.S. Pat. No. 6,192,939 and No. 6,284,113 and by European WO 01/01025 and WO 01/12327. However, those methods involve in either electrokinetic transport mechanisms or controlling applied pressure or vacuum. Therefore, there are difficulties either in device fabrication or in accurate control of complex fluidic systems.
The present invention provides an integrated microfluidic system and the method to use it to control the delivery and mixing of transport fluids in a lab-on-a-chip device. This method takes advantages of a thermally-responsive fluid as the transport fluid, and uses integrated heating elements on the chip to control the flow rate come in and out of a fluid mixing or reaction element. The system is simple to fabricated and easy to use.
It is an object of this invention to provide a microfluidic system for controlling the delivery and mixing of materials through the microfluidic system and a method for controlling the delivery and mixing of materials through the microfluidic system without any mechanical actuation or moving parts.
It is another object of this invention to provide a microfluidic system using multiple integrated heaters in combined with a specially formulated thermally-responsive solution to control fluids from multiple in-let channels passing through a micro-fluidic mixing or reaction element to multiple out-let channels avoiding any mechanical actuation.
It is yet another object of this invention to provide a microfluidic delivery and mixing system that can be readily fabricated using standard CMOS fabrication technology in the semiconductor industry.
According to a feature of the present invention, a microfluidic system is provided for controlling delivery and mixing of thermally-responsive fluids. A plurality of microfluidic inlet channels open into a mixing chamber. A valve is associated with each of the inlet channels for controlling the flow of the thermally-responsive fluids through the inlet channels. The valves include a heater in thermal contact with at least a portion of the associated inlet channel, whereby the viscosity of the thermally-responsive fluids can selectively be controlled by heat to cause a change in flow of the thermally-responsive fluids through the inlet channels. A plurality of microfluidic outlet channels may be provided for transporting mixed fluids from the mixing chamber. A valve associated with each of the outlet channels controls the flow of the mixed thermally-responsive fluids through the outlet channels. These valves also include a heater in contact with at least a portion of the associated outlet channel, whereby said mixed thermally-responsive fluids can be directed from the mixing chamber selectively through each outlet channel.